Depth profile of concentration of deep-level impurities in vapor-phase epitaxial gallium-arsenide grown under various arsenic vapor pressures

Abstract

Vapor‐phase homoepitaxial GaAs films were grown by using the Ga–As–HCl–H₂ reaction system under various values of arsenic pressure P_As. Growth rate, electron mobility, shallow donor density N_D, shallow acceptor density N_A, and deep‐level impurity density N_T were measured and found to be in close relationship with P_As. Measurements of the concentration profile N_T(x) of the deep‐level impurities in the film were carried out by using the modified version of the transient C‐V method developed by Senechal et al. Main results are (i) The energy level of these impurities is 0.89 eV from the conduction band, which is independent of growth condition, species of substrate and/or the depth position x in the film. (ii) Independently of the occurrence of the abnormal high‐resistivity layer at the film‐substrate interface, the concentration N_T(x) in the region within a few microns from the interface is rather lower than that in the region far from it. (iii) In the film grown on the undoped substrate, the density N_T(x) peaks at the transition point from the initial high‐resistivity layer to the steady‐state layer, whereas in the film grown on the Te‐doped or Sn‐doped substrate where the high‐resistivity layer does not appear, no peak occurs in the profile N_T(x). The energy level of 0.89 eV suggests these impurities to be copper. Most of the characteristics in the depth profile N_T(x) mentioned above can be understood by taking into account the complicated behavior of copper in GaAs.